Conventionally, there are known speaker systems as a cone type as shown in FIG. 1 and a dome-type as shown in FIG. 2.
That is, in FIG. 1, a voice coil 3 is fixed on the top of a cone of a vibration plate 2 attached to a frame 1 through an edge of the vibration plate 2. The voice coil 3 generates a driving force in a magnetic gap owing to a sound current flowing through the voice coil 3, so that the vibration plate 2 is vibrated so as to generate a sound pressure.
On the other hand, a magnetic circuit generates magnetic flux in the magnetic gap and is arranged such that a top plate 4, a magnet 5, and a pole yoke 6 are made to adhere with one another by means of a bonding agent. The top plate 4 is fixed to the frame 1 by screws or by means of caulking. The frame 1 is attached at its outer circumference to a baffle board 7 of a speaker cabinet by means of screws.
In the dome-type speaker system shown in FIG. 2, a flange 8 performs the same task as the frame 1 of the cone type speaker system shown in FIG. 1. That is, the flange 8 is equivalent to the frame 1.
However, since the respective conventional speaker system has been arranged in such a manner as described above, the magnetic circuit is vibrated slightly owing to the reaction of a vibrating system constituted by the vibration plate, the voice coil, the edge, and the damper simultaneously with the generation of the sound pressure owing to the driving force generated in the voice coil.
The vibrations are transmitted also to the frame to vibrate the baffle board to radiate unnecessary sound, thereby causing distortion.